Hi,
I am going to share some measurements that I made using an IET LOM-510A Micro-Ohmmeter.
Link:
https://www.ietlabs.com/lom-510.htmlThis may be one of the best instruments available for measuring very small resistances.
The 4W-shorts are directional. The best results are obtained if you connected
Source + to Source - with a thick trace
Sense+ to Sense- with a thick trace
a short, wide trace connecting the two together.
I am going to call this the preferred orientation. The other orientation I will call non-preferred.
Keithley DesignPreferred Orientation
![4-wire short - 2020](https://www.eevblog.com/forum/index.php?action=dlattach;topic=255424.0;attach=1084980;image)
![](https://www.eevblog.com/forum/projects/4-wire-short-2020/?action=dlattach;attach=1084980;image)
This reads 0.000 m
![Ohms \$\Omega\$](https://www.eevblog.com/forum/Smileys/default/omega.gif)
This make sense, you are measuring a very short, very wide track.
Non-Preferred Orientation
![4-wire short - 2020](https://www.eevblog.com/forum/index.php?action=dlattach;topic=255424.0;attach=1084984;image)
![](https://www.eevblog.com/forum/projects/4-wire-short-2020/?action=dlattach;attach=1084984;image)
This measures 20.23 m
![Ohms \$\Omega\$](https://www.eevblog.com/forum/Smileys/default/omega.gif)
You are measure a long, thin track.
Universal Design (Keithley Style)Preferred orientation
![4-wire short - 2020](https://www.eevblog.com/forum/index.php?action=dlattach;topic=255424.0;attach=1084988;image)
![](https://www.eevblog.com/forum/projects/4-wire-short-2020/?action=dlattach;attach=1084988;image)
This is a very wide, very short track.
Non-Preferred Orientation
![4-wire short - 2020](https://www.eevblog.com/forum/index.php?action=dlattach;topic=255424.0;attach=1084992;image)
![](https://www.eevblog.com/forum/projects/4-wire-short-2020/?action=dlattach;attach=1084992;image)
28.17 m\$\Omega\$. This makes sense, the track is a little longer than the design above.
Felixd DesignPreferred orientation
![4-wire short - 2020](https://www.eevblog.com/forum/index.php?action=dlattach;topic=255424.0;attach=1084996;image)
![](https://www.eevblog.com/forum/projects/4-wire-short-2020/?action=dlattach;attach=1084996;image)
4 u
![Ohms \$\Omega\$](https://www.eevblog.com/forum/Smileys/default/omega.gif)
(4 Micro Ohms)
Non-Preferred Orientation
![4-wire short - 2020](https://www.eevblog.com/forum/index.php?action=dlattach;topic=255424.0;attach=1085000;image)
![](https://www.eevblog.com/forum/projects/4-wire-short-2020/?action=dlattach;attach=1085000;image)
1.389 m
![Ohms \$\Omega\$](https://www.eevblog.com/forum/Smileys/default/omega.gif)
The 'X' pattern is not as sensitive to the orientation as the Keithley 'H' style design. But, it is not as good as the Keithley 'H' in the preferred orientation.
Note:The Datron 1281 requires a different 'H' design than the HP 3457A. The 'H' has to be rotated 90
o.
Regards,
Jay_Diddy_B